DOCSLIB.ORG

The Solar Neighborhood XVII: Parallax Results from the CTIOPI 0.9 M Program--Twenty New Members of the RECONS 10 Parsec Sample

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Solar Neighborhood XVII: Parallax Results from the CTIOPI 0.9 M Program--Twenty New Members of the RECONS 10 Parsec Sample accepted to the Astronomical Journal 31 July 2006 The Solar Neighborhood XVII: Parallax Results from the CTIOPI 0.9 m Program – Twenty New Members of the RECONS 10 Parsec Sample Todd J. Henry1, Wei-Chun Jao1, John P. Subasavage1, and Thomas D. Beaulieu1 Georgia State University, Atlanta, GA 30302-4106 [email protected], [email protected], [email protected], [email protected] Philip A. Ianna1 University of Virginia, Charlottesville, VA 22903 [email protected] and Edgardo Costa1, Ren´eA. M´endez1 Universidad de Chile, Santiago, Chile [email protected], [email protected] ABSTRACT arXiv:astro-ph/0608230v1 10 Aug 2006 Astrometric measurements for 25 red dwarf systems are presented, including the first definitive trigonometric parallaxes for 20 systems within 10 pc of the Sun, the horizon of the RECONS sample. The three nearest systems that had no previous trigonometric parallaxes (other than perhaps rough preliminary efforts) are SO 0253+1652 (3.84 ± 0.04 pc, the 23rd nearest system), SCR 1845-6357 AB (3.85 ± 0.02 pc, 24th), and LHS 1723 (5.32 ± 0.04 pc, 56th). In total, seven of the systems reported here rank among the nearest 100 stellar systems. Sup- porting photometric and spectroscopic observations have been made to provide 1Visiting Astronomer, Cerro Tololo Inter-American Observatory. CTIO is operated by AURA, Inc. under contract to the National Science Foundation. –2– full characterization of the systems, including complete VRIJHKs photometry and spectral types. A study of the variability of 27 targets reveals six obvious variable stars, including GJ 1207, for which we observed a flare event in the V band that caused it to brighten by 1.7 mag. Improved parallaxes for GJ 54 AB and GJ 1061, both important members of the 10 pc sample, are also reported. Definitive parallaxes for GJ 1001 A, GJ 633, and GJ 2130 ABC, all of which have been reported to be within 10 pc, indicate that they are beyond 10 pc. From the analysis of systems with (previously) high trigonometric parallax errors, we conclude that parallaxes with errors in excess of 10 mas are insufficiently reliable for inclusion in the RECONS sample. The cumulative total of new additions to the 10 pc sample since 2000 is now 34 systems — 28 by the RECONS team and six by other groups. This total represents a net increase of 16% in the number of stellar systems reliably known to be nearer than 10 pc. Subject headings: surveys — astrometry — stars: distances — stars: low mass, brown dwarfs — stars: statistics — solar neighborhood 1. Introduction Trigonometric parallax determinations provide one of the most fundamental measures of the cosmos. Their beauty lies in their simplicity: they are based only on geometric techniques and are the straightforward result of the Earth orbiting the Sun. Trigonometric parallaxes help define solar neighborhood membership, allow for accurate masses calculations in binary systems, provide distances to fundamental stellar clusters, and supply benchmarks for stellar population studies in the Milky Way and nearby galaxies. With concerted effort, trigonometric parallaxes with accuracies of ∼1 milliarcsecond are possible, yielding distances good to 10% even at 100 pc, and allow astronomers to create an accurate three-dimensional map of the nearby Galaxy. Much like early explorers’ discoveries created a more complete map of our Earth, accurate trigonometric parallaxes create a more detailed picture of the solar neighborhood, filling in the blank regions of nearby space. van Altena et al. (1995) compiled decades of ground-based work by dedicated as- trometrists in The General Catalogue of Trigonometric Stellar Parallaxes (also known as the “Yale Parallax Catalog”, hereafter, YPC). The YPC includes 15994 total trigonometric parallaxes for 8112 stars measured using photographic plates and CCDs published before the end of 1995. The Hipparcos space mission, launched in August 1989, provided ∼118,000 parallaxes (Perryman et al. 1997; ESA 1997, hereafter HIP), and was essentially complete –3– for stars with V = 7.3 − 9.0, while reaching to observe a few dozen stars even fainter than V ∼13. However, Hipparcos could not measure most nearby white, red, and brown dwarfs, which comprise more than 80% of the solar neighborhood population, and many of these systems have not yet had their distances measured via ground-based trigonometric parallax efforts. Here we present results for nearby star systems observed during our Cerro Tololo Inter- american Observatory Parallax Investigation (CTIOPI). Twenty systems are new members of the Research Consortium on Nearby Stars (RECONS) sample, meeting the RECONS requirements that they have trigonometric parallaxes, πtrig, larger than 100 mas with errors less than 10 mas (see section 6.1). We provide a brief dossier for each new systems, including VRIJHKs photometry and spectral types. We also provide improved πtrig for two additional important systems previously known to be within 10 pc, GJ 54 AB and GJ 1061, and for three systems that have reported πtrig larger than 100 mas, but which, in truth, lie beyond the 10 pc horizon. In total, we report 27 new trigonometric parallax measurements for 25 systems. 2. CTIOPI and Other Recent Trigonometric Parallax Efforts Since the publication of the YPC and HIP results, only ∼250 ground-based parallaxes and a handful space-based parallaxes from HST (e.g., Benedict et al. 1999) have been pub- lished in the refereed literature. We provide a comprehensive tally of ground-based trigono- metric parallax measurements published for new RECONS systems in Table 1, since the 1995 cutoff date of the YPC.1 The transition of data acquisition techniques from photographic plates to CCDs and infrared arrays is nearly complete, although approximate parallaxes for the nearest objects can still be derived from large archival databases that include scanned plates (Deacon & Hambly 2001; Teegarden et al. 2003; Deacon et al. 2005). These parallaxes are useful but necessarily crude, given the limited number of epochs available and the coarse plate scales. The most recent change in parallax work is the advent of IR arrays (e.g., Vrba et al. 2004). Our CCD parallax effort, CTIOPI, began as an NOAO Surveys Program in 1999 August 1All parallaxes in Reid et al. (2000) were updated in Dahn et al. (2002). Two objects, TVLM 513-46546 (Tinney et al. 1995; Dahn et al. 2002) and 2MA 1047+2124, (Tinney et al. 2003; Vrba et al. 2004) are borderline objects — the Tinney parallaxes place the objects closer than 10 pc whereas the Dahn and Vrba USNO parallaxes place them beyond 10 pc. Weighted means of the two values for each object yield distances larger than 10 pc, so neither is included as a new 10 pc system in Table 1. –4– using both the 0.9 m and 1.5 m telescopes at CTIO, and has continued on the 0.9 m as part of the SMARTS (Small and Moderate Aperture Research Telescope System) Consortium be- ginning in 2003 February. The primary goals of CTIOPI are to discover and characterize any nearby objects that remain unidentified in the solar neighborhood — primarily red dwarfs, brown dwarfs, and white dwarfs. Although CTIOPI concentrates on southern hemisphere systems, we also target important nearby star candidates as far north as δ = +30. Most of the stellar systems observed during CTIOPI have been selected because available astro- metric data (high proper motions, crude parallaxes) or photometric/spectroscopic distance estimates indicate that they might be within 25 pc, the horizon of the Catalog of Nearby Stars (Gliese & Jahreiß 1991) and NStars (Henry et al. 2003) compendia. Objects possibly nearer than 10 pc are given highest priority. The parallaxes we measure typically have errors less than 3 mas, corresponding to distance errors of only 1–3% for systems within 10 pc. At the beginning of 2006, we continued to observe roughly two-thirds of the more than 400 systems targeted for parallax measurements during the 0.9 m program. Under SMARTS, we have expanded CTIOPI to carry out a program to search for low mass companions to nearby stars, called ASPENS (Astrometric Search for Planets Encircling Nearby Stars), in collaboration with David Koerner at Northern Arizona University. This paper is the fourth publication in The Solar Neighborhood series that includes CTIOPI parallaxes. Jao et al. (2005) presented 46 parallaxes for high proper motion systems observed at the 0.9 m. Costa et al. (2005) and Costa et al. (2006, AJ in press) presented 62 total parallaxes for fainter systems, including brown dwarf candidates, observed at the 1.5 m. In this paper, we concentrate on systems observed at the 0.9 m that were candidates for the 10 pc sample and present 27 total parallaxes. 3. Photometry Because of the significant investment in observing time required to determine a trigono- metric parallax — roughly one integrated night over at least two years for each target — it is prudent to obtain characterization photometry of nearby star candidates before placing them on the astrometric program. As shown in Henry et al. (2004), the combination of 2 VJ , RKC and IKC (hereafter, without subscripts) photometry and infrared J, H, and Ks photometry from 2MASS can be used in a suite of color-absolute magnitude relations to estimate distances of main sequence stars with 15% accuracy. 2 Subscript: J = Johnson, KC = Kron-Cousins. The central wavelengths for VJ , RKC and IKC are 5475A,˚ 6425A˚ and 8075A,˚ respectively. –5– V RI photometry is reported in Table 2. Two names are often given, followed by the new optical V RI photometry and the number of nights on which observations were taken during CTIOPI. Photometry was acquired at the CTIO 0.9 m using the same filter and detector combination used for the astrometry frames (see section 5 for details of the instru- mental setup).
Load more

Recommended publications
  • 100 Closest Stars Designation R.A
    100 closest stars Designation R.A. Dec. Mag. Common Name 1 Gliese+Jahreis 551 14h30m –62°40’ 11.09 Proxima Centauri Gliese+Jahreis 559 14h40m –60°50’ 0.01, 1.34 Alpha Centauri A,B 2 Gliese+Jahreis 699 17h58m 4°42’ 9.53 Barnard’s Star 3 Gliese+Jahreis 406 10h56m 7°01’ 13.44 Wolf 359 4 Gliese+Jahreis 411 11h03m 35°58’ 7.47 Lalande 21185 5 Gliese+Jahreis 244 6h45m –16°49’ -1.43, 8.44 Sirius A,B 6 Gliese+Jahreis 65 1h39m –17°57’ 12.54, 12.99 BL Ceti, UV Ceti 7 Gliese+Jahreis 729 18h50m –23°50’ 10.43 Ross 154 8 Gliese+Jahreis 905 23h45m 44°11’ 12.29 Ross 248 9 Gliese+Jahreis 144 3h33m –9°28’ 3.73 Epsilon Eridani 10 Gliese+Jahreis 887 23h06m –35°51’ 7.34 Lacaille 9352 11 Gliese+Jahreis 447 11h48m 0°48’ 11.13 Ross 128 12 Gliese+Jahreis 866 22h39m –15°18’ 13.33, 13.27, 14.03 EZ Aquarii A,B,C 13 Gliese+Jahreis 280 7h39m 5°14’ 10.7 Procyon A,B 14 Gliese+Jahreis 820 21h07m 38°45’ 5.21, 6.03 61 Cygni A,B 15 Gliese+Jahreis 725 18h43m 59°38’ 8.90, 9.69 16 Gliese+Jahreis 15 0h18m 44°01’ 8.08, 11.06 GX Andromedae, GQ Andromedae 17 Gliese+Jahreis 845 22h03m –56°47’ 4.69 Epsilon Indi A,B,C 18 Gliese+Jahreis 1111 8h30m 26°47’ 14.78 DX Cancri 19 Gliese+Jahreis 71 1h44m –15°56’ 3.49 Tau Ceti 20 Gliese+Jahreis 1061 3h36m –44°31’ 13.09 21 Gliese+Jahreis 54.1 1h13m –17°00’ 12.02 YZ Ceti 22 Gliese+Jahreis 273 7h27m 5°14’ 9.86 Luyten’s Star 23 SO 0253+1652 2h53m 16°53’ 15.14 24 SCR 1845-6357 18h45m –63°58’ 17.40J 25 Gliese+Jahreis 191 5h12m –45°01’ 8.84 Kapteyn’s Star 26 Gliese+Jahreis 825 21h17m –38°52’ 6.67 AX Microscopii 27 Gliese+Jahreis 860 22h28m 57°42’ 9.79,
    [Show full text]
  • RECONS Discoveries Within 10 Parsecs
    The Astronomical Journal, 155:265 (23pp), 2018 June https://doi.org/10.3847/1538-3881/aac262 © 2018. The American Astronomical Society. All rights reserved. The Solar Neighborhood XLIV: RECONS Discoveries within 10 parsecs Todd J. Henry1,8, Wei-Chun Jao2,8 , Jennifer G. Winters3,8 , Sergio B. Dieterich4,8, Charlie T. Finch5,8, Philip A. Ianna1,8, Adric R. Riedel6,8 , Michele L. Silverstein2,8 , John P. Subasavage7,8 , and Eliot Halley Vrijmoet2 1 RECONS Institute, Chambersburg, PA 17201, USA; [email protected], [email protected] 2 Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30302, USA; [email protected], [email protected], [email protected] 3 Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA; [email protected] 4 Department of Terrestrial Magnetism, Carnegie Institution for Science, Washington, DC 20015, USA; [email protected] 5 Astrometry Department, U.S. Naval Observatory, Washington, DC 20392, USA; charlie.fi[email protected] 6 Space Telescope Science Institute, Baltimore, MD 21218, USA; [email protected] 7 United States Naval Observatory, Flagstaff, AZ 86001, USA; [email protected] Received 2018 April 12; revised 2018 April 27; accepted 2018 May 1; published 2018 June 4 Abstract We describe the 44 systems discovered to be within 10 pc of the Sun by the RECONS team, primarily via the long- term astrometry program at the CTIO/SMARTS 0.9 m that began in 1999. The systems—including 41 with red dwarf primaries, 2 white dwarfs, and 1 brown dwarf—have trigonometric parallaxes greater than 100 mas, with errors of 0.4–2.4 mas in all but one case.
    [Show full text]
  • The Solar Neighborhood XLIV: RECONS Discoveries Within 10 Parsecs
    The Astronomical Journal, 155:265 (23pp), 2018 June https://doi.org/10.3847/1538-3881/aac262 © 2018. The American Astronomical Society. All rights reserved. The Solar Neighborhood XLIV: RECONS Discoveries within 10 parsecs Todd J. Henry1,8, Wei-Chun Jao2,8 , Jennifer G. Winters3,8 , Sergio B. Dieterich4,8, Charlie T. Finch5,8, Philip A. Ianna1,8, Adric R. Riedel6,8 , Michele L. Silverstein2,8 , John P. Subasavage7,8 , and Eliot Halley Vrijmoet2 1 RECONS Institute, Chambersburg, PA 17201, USA; [email protected], [email protected] 2 Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30302, USA; [email protected], [email protected], [email protected] 3 Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA; [email protected] 4 Department of Terrestrial Magnetism, Carnegie Institution for Science, Washington, DC 20015, USA; [email protected] 5 Astrometry Department, U.S. Naval Observatory, Washington, DC 20392, USA; charlie.fi[email protected] 6 Space Telescope Science Institute, Baltimore, MD 21218, USA; [email protected] 7 United States Naval Observatory, Flagstaff, AZ 86001, USA; [email protected] Received 2018 April 12; revised 2018 April 27; accepted 2018 May 1; published 2018 June 4 Abstract We describe the 44 systems discovered to be within 10 pc of the Sun by the RECONS team, primarily via the long- term astrometry program at the CTIO/SMARTS 0.9 m that began in 1999. The systems—including 41 with red dwarf primaries, 2 white dwarfs, and 1 brown dwarf—have trigonometric parallaxes greater than 100 mas, with errors of 0.4–2.4 mas in all but one case.
    [Show full text]
  • 20 NEW MEMBERS of the RECONS 10 PARSEC SAMPLE Todd J
    THE SOLAR NEIGHBORHOOD. XVII. PARALLAX RESULTS FROM THE CTIOPI 0.9 m PROGRAM: 20 NEW MEMBERS OF THE RECONS 10 PARSEC SAMPLE Todd J. Henry,1 Wei-Chun Jao,1 John P. Subasavage,1 and Thomas D. Beaulieu1 Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30302-4106; [email protected], [email protected], [email protected], [email protected] Philip A. Ianna1 Department of Physics and Astronomy, University of Virginia, Charlottesville, VA 22903; [email protected] and Edgardo Costa1 and Rene´ A. Me´ndez1 Departamento de Astronom«õa, Universidad de Chile, Santiago, Chile; [email protected], [email protected] ABSTRACT Astrometric measurements for 25 red dwarf systems are presented, including the first definitive trigonometric par- allaxes for 20 systems within 10 pc of the Sun, the horizon of the RECONS sample. The three nearest systems that had no previous trigonometric parallaxes (other than perhaps rough preliminary efforts) are SO 0253+1652 (3:84 Æ 0:04 pc, the 23rd nearest system), SCR 1845À6357 AB (3:85 Æ 0:02 pc, 24th nearest), and LHS 1723 (5:32 Æ 0:04 pc, 56th nearest). In total, seven of the systems reported here rank among the nearest 100 stellar systems. Sup- porting photometric and spectroscopic observations have been made to provide full characterization of the systems, including complete VRIJHKs photometry and spectral types. A study of the variability of 27 targets reveals six ob- vious variable stars, including GJ 1207, for which we observed a flare event in the V band that caused it to brighten by 1.7 mag.
    [Show full text]
  • Detectability of Atmospheric Features of Earth-Like Planets in the Habitable
    Astronomy & Astrophysics manuscript no. Wunderlich_etal_2019_arxiv c ESO 2019 May 8, 2019 Detectability of atmospheric features of Earth-like planets in the habitable zone around M dwarfs Fabian Wunderlich1, Mareike Godolt1, John Lee Grenfell2, Steffen Städt3, Alexis M. S. Smith2, Stefanie Gebauer2, Franz Schreier3, Pascal Hedelt3, and Heike Rauer1; 2; 4 1 Zentrum für Astronomie und Astrophysik, Technische Universität Berlin, Hardenbergstraße 36, 10623 Berlin, Germany e-mail: [email protected] 2 Institut für Planetenforschung, Deutsches Zentrum für Luft- und Raumfahrt, Rutherfordstraße 2, 12489 Berlin, Germany 3 Institut für Methodik der Fernerkundung, Deutsches Zentrum für Luft- und Raumfahrt, 82234 Oberpfaffenhofen, Germany 4 Institut für Geologische Wissenschaften, Freie Universität Berlin, Malteserstr. 74-100, 12249 Berlin, Germany ABSTRACT Context. The characterisation of the atmosphere of exoplanets is one of the main goals of exoplanet science in the coming decades. Aims. We investigate the detectability of atmospheric spectral features of Earth-like planets in the habitable zone (HZ) around M dwarfs with the future James Webb Space Telescope (JWST). Methods. We used a coupled 1D climate-chemistry-model to simulate the influence of a range of observed and modelled M-dwarf spectra on Earth-like planets. The simulated atmospheres served as input for the calculation of the transmission spectra of the hy- pothetical planets, using a line-by-line spectral radiative transfer model. To investigate the spectroscopic detectability of absorption bands with JWST we further developed a signal-to-noise ratio (S/N) model and applied it to our transmission spectra. Results. High abundances of methane (CH4) and water (H2O) in the atmosphere of Earth-like planets around mid to late M dwarfs increase the detectability of the corresponding spectral features compared to early M-dwarf planets.
    [Show full text]
  • Further Defining Spectral Type" Y" and Exploring the Low-Mass End of The
    Submitted to The Astrophysical Journal Further Defining Spectral Type “Y” and Exploring the Low-mass End of the Field Brown Dwarf Mass Function J. Davy Kirkpatricka, Christopher R. Gelinoa, Michael C. Cushingb, Gregory N. Macec Roger L. Griffitha, Michael F. Skrutskied, Kenneth A. Marsha, Edward L. Wrightc, Peter R. Eisenhardte, Ian S. McLeanc, Amanda K. Mainzere, Adam J. Burgasserf , C. G. Tinneyg, Stephen Parkerg, Graeme Salterg ABSTRACT We present the discovery of another seven Y dwarfs from the Wide-field In- frared Survey Explorer (WISE). Using these objects, as well as the first six WISE Y dwarf discoveries from Cushing et al., we further explore the transition between spectral types T and Y. We find that the T/Y boundary roughly coincides with the spot where the J − H colors of brown dwarfs, as predicted by models, turn back to the red. Moreover, we use preliminary trigonometric parallax measure- ments to show that the T/Y boundary may also correspond to the point at which the absolute H (1.6 µm) and W2 (4.6 µm) magnitudes plummet. We use these discoveries and their preliminary distances to place them in the larger context of the Solar Neighborhood. We present a table that updates the entire stellar and substellar constinuency within 8 parsecs of the Sun, and we show that the cur- rent census has hydrogen-burning stars outnumbering brown dwarfs by roughly a factor of six. This factor will decrease with time as more brown dwarfs are iden- tified within this volume, but unless there is a vast reservoir of cold brown dwarfs arXiv:1205.2122v1 [astro-ph.SR] 9 May 2012 aInfrared Processing and Analysis Center, MS 100-22, California Institute of Technology, Pasadena, CA 91125; [email protected] bDepartment of Physics and Astronomy, MS 111, University of Toledo, 2801 W.
    [Show full text]
  • The Solar Neighborhood. Xxviii. the Multiplicity Fraction of Nearby Stars from 5 to 70 Au and the Brown Dwarf Desert Around M Dwarfs
    The Astronomical Journal, 144:64 (19pp), 2012 August doi:10.1088/0004-6256/144/2/64 C 2012. The American Astronomical Society. All rights reserved. Printed in the U.S.A. THE SOLAR NEIGHBORHOOD. XXVIII. THE MULTIPLICITY FRACTION OF NEARBY STARS FROM 5 TO 70 AU AND THE BROWN DWARF DESERT AROUND M DWARFS Sergio B. Dieterich1, Todd J. Henry1, David A. Golimowski2,JohnE.Krist3, and Angelle M. Tanner4 1 Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30302-4106, USA; [email protected] 2 Space Telescope Science Institute, Baltimore, MD 21218, USA 3 Jet Propulsion Laboratory, Pasadena, CA 91109, USA 4 Department of Physics and Astronomy, Mississippi State University, Starkville, MS 39762, USA Received 2012 February 13; accepted 2012 May 29; published 2012 July 16 ABSTRACT We report on our analysis of Hubble Space Telescope/NICMOS snapshot high-resolution images of 255 stars in 201 systems within ∼10 pc of the Sun. Photometry was obtained through filters F110W, F180M, F207M, and F222M using NICMOS Camera 2. These filters were selected to permit clear identification of cool brown dwarfs through methane contrast imaging. With a plate scale of 76 mas pixel−1, NICMOS can easily resolve binaries with subarcsecond separations in the 19.5×19.5 field of view. We previously reported five companions to nearby M and L dwarfs from this search. No new companions were discovered during the second phase of data analysis presented here, confirming that stellar/substellar binaries are rare. We establish magnitude and separation limits for which companions can be ruled out for each star in the sample, and then perform a comprehensive sensitivity and completeness analysis for the subsample of 138 M dwarfs in 126 systems.
    [Show full text]
  • Theoretical Astroparticle Physics
    Theoretical Astroparticle Physics Contents 1. Topics 1339 2. Participants 1341 2.1. ICRANetparticipants. 1341 2.2. Pastcollaborators . 1341 2.3. Ongoingcollaborations. 1342 2.4. Students ............................... 1342 3. Brief description 1343 3.1. Electron-positronplasma. 1343 3.1.1. Thermalization of mildly relativistic plasma with pro- tonloading ......................... 1343 3.1.2. Pairplasmarelaxationtimescales. 1344 3.1.3. HydrodynamicphaseofGRBsources . 1345 3.2. Neutrinosincosmology . 1345 3.2.1. Massive neutrino and structure formation . 1347 3.2.2. CellularstructureoftheUniverse . 1347 3.2.3. LeptonasymmetryoftheUniverse . 1348 3.2.4. MassVaryingNeutrinos . 1348 3.3. IndirectDetectionofDarkMatter . 1349 3.4. AlternativeCosmologicalModels. 1350 4. Publications 1353 4.1. Publicationsbefore2005 . 1353 4.2. Publications(2005-2008) . 1356 4.3. Publications(2009) . 1362 4.4. Invitedtalksatinternationalconferences . 1365 5. APPENDICES 1369 A. Pair plasma relaxation timescales 1371 B.HydrodynamicphaseofGRBsources 1379 B.1. Introduction ............................. 1379 B.2. Kineticandhydrodynamicalphases . 1381 B.3. Physicalevolution. 1383 1335 Contents B.4. Results ................................ 1385 B.4.1. Constant baryonic distribution profile . 1385 B.4.2. c)Hybridprofile . 1387 B.5. Conclusions ............................. 1389 B.6. Numericalapproach . 1390 B.6.1. Finitedifferenceformofequations . 1392 B.6.2. Numericalissues . 1393 B.7. test .................................. 1395 B.7.1. a)Piran’sprofile . 1395 C. Cosmological
    [Show full text]
  • Filling the Brown Dwarf Census of the Solar Neighbourhood
    201: Milky Way and the Local Volume Filling the brown dwarf census of the Solar neighbourhood Ralf-Dieter Scholz, Gabriel Bihain, Jesper Storm, Olivier Schnurr Summary Many brown dwarf (BD) neighbours have recently been discovered thanks to new surveys in the mid- and near-infrared (MIR,NIR) but the number of red dwarfs is also still growing (Fig.1). The number of BDs is now about six times lower than that of stars in the same volume (Kirkpatrick et al. 2012, see also Fig.2). Our aim is to detect and classify new nearby BDs, contributing to the eventual completeness of their census in the immediate solar neighbourhood. We combine multi-epoch data from optical, NIR, and MIR surveys (Fig.3) to detect BD neighbours of the Sun by their high proper motion (HPM), concentrating on relatively bright MIR (w2 < 13.5) BD candidates from the Wide-Field Infrared Survey Explorer (WISE). With low-resolution NIR spectroscopy (Fig.4) we classify the new BDs and estimate their distances and velocities. Fig.2: Update for the immediate solar neighbourhood with results from WISE. Among the BDs, there are some still lacking accurate trigonometric parallaxes, for which spectroscopic distances are used. Among the marked AIP discoveries, there are two M dwarfs, LHS 2090 (Scholz et al. 2001) and L 449-1 (Scholz et al. 2005), that were already listed in old HPM catalogues, and five T dwarfs, ε Indi Ba,Bb (Scholz et al. 2003, McCaughrean et al. 2004), WISE J0254+0223 and WISE J1741+2553 (Scholz et al. 2011), and WISE J0521+1025 (Bihain et al.
    [Show full text]
  • Science Highlights
    Science Highlights Low-Luminosity, Compact Accretion Sources in the Galaxy Josh Grindlay (Harvard Observatory and CfA) ccretion onto compact stellar objects (white dwarfs, careful treatment of astrometry for optical identifi cations, neutron stars, and black holes) from companions in and derived source fl uxes for a range of model spectra close binaries is the primary beacon for study of the and absorption columns for both the source number-fl ux Aastrophysics of the extreme: from endpoints of stellar and distribution, logN-logS, and X-ray spectral classifi cation. binary evolution, to the physical processes in the extremes of gravity, radiation, or magnetic fi elds. Accretion from the Initial ChaMPlane results were given for logN-logS in several interstellar medium on the presumed still larger population Galactic fi elds (Grindlay et al. 2003, AN, 324, 57), as well as an of isolated compact objects should, at least for relatively early description of the Mosaic imaging identifi cation survey more massive and low-velocity stellar black holes, also be (Zhao et al. 2003, AN, 324, 176). Th e survey has now achieved observable in certain conditions, yet never has been. Given nearly its original goal of ~100 Chandra ACIS-I or ACIS-S the fundamental role that accretion plays in so many key galactic plane fi elds, with in fact 94 now selected (through problems of interest in current astrophysics, it is surprising Chandra cycle 6). Th ese have |b| ≤ 12o, exposure times that the space density and luminosity function(s) of the most ≥12 ksec (most are >20–30 ksec), and are selected to avoid common accretion-powered compact objects—white dwarfs dense clusters or bright diff use optical emission, and accreting from low-mass stellar companions, or cataclysmic (if possible) to have a minimum hydrogen column density in variables (CVs)—has not been measured to better than a order to maximize the detection and subsequent identifi cation factor of ~10 in the solar neighborhood, and they have even of faint point sources.
    [Show full text]
  • Spectroscopy of Faint, Red NLTT Dwarfs
    Draft: August 4, 2003 Meeting the Cool Neighbors VII: Spectroscopy of faint, red NLTT dwarfs I. Neill Reid1 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218; and Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104; [email protected] Kelle L. Cruz1, Peter Allen1, F. Mungall1 Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104; [email protected] D. Kilkenny South African Astronomical Observatory, P.O. Box 9, Observatory 7935, South Africa James Liebert1 Department of Astronomy and Steward Observatory, University of Arizona, Tucson, AZ 85721; [email protected] Suzanne L. Hawley, Oliver J. Fraser, Kevin R. Covey Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 Patrick Lowrance1 IPAC, MS 100-22 Caltech, 770 S. Wilson Ave., Pasadena, CA 91125 ABSTRACT We present low-resolution optical spectroscopy and BVRI photometry of 453 can- didate nearby stars drawn from the NLTT proper motion catalogue. The stars were selected based on optical/near-infrared colours, derived by combining the NLTT pho- tographic data with photometry from the 2MASS Second Incremental Data Release. Based on the derived photometric and spectroscopic parallaxes, we identify 111 stars as lying within 20 parsecs of the Sun, including 9 stars with formal distance estimates 1Visiting Astronomer, Kitt Peak National Observatory, NOAO, which is operated by AURA under cooperative agreement with the NSF. { 2 { of less than 10 parsecs. A further 53 stars have distance estimates within 1σ of our 20- parsec limit. Almost all of those stars are additions to the nearby star census.
    [Show full text]
  • Search for Nearby Stars Among Proper Motion Stars Selected by Optical-To
    Astronomy & Astrophysics manuscript no. (will be inserted by hand later) Search for nearby stars among proper motion stars selected by optical-to-infrared photometry I. Discovery of LHS 2090 at spectroscopic distance of d ∼ 6 pc R.-D. Scholz1, H. Meusinger2,⋆, and H. Jahreiß3 1 Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D–14482 Potsdam, Germany e-mail: [email protected] 2 Th¨uringer Landessternwarte Tautenburg, D–07778 Tautenburg, Germany e-mail: [email protected] 3 Astronomisches Rechen-Institut, M¨onchhofstraße 12-14, D–69120 Heidelberg, Germany e-mail: [email protected] Received ; accepted Abstract. We present the discovery of a previously unknown very nearby star - LHS 2090 at a distance of only d = 6 pc. In order to find nearby (i.e. d < 25 pc) red dwarfs, we re-identified high proper motion stars (µ > 0.18 arcsec/yr) from the NLTT catalogue (Luyten 1979-1980) in optical Digitized Sky Survey data for two different epochs and in the 2MASS data base. Only proper motion stars with large R − Ks colour index and with relatively bright infrared magnitudes (Ks < 10) were selected for follow-up spectroscopy. The low- resolution spectrum of LHS 2090 and its large proper motion (0.79 arcsec/yr) classify this star as an M6.5 dwarf. The resulting spectroscopic distance estimate from comparing the infrared JHKs magnitudes of LHS 2090 with absolute magnitudes of M6.5 dwarfs is 6.0 ± 1.1 pc assuming an uncertainty in absolute magnitude of ±0.4 mag. Key words. astrometry and celestial mechanics: astrometry – astronomical data base: surveys – stars: late-type – stars: low mass, brown dwarfs 1.
    [Show full text]